Solve y′=−yy' = -yy′=−y with y(0)=5y(0) = 5y(0)=5.
y=5e−xy = 5e^{-x}y=5e−x
y=5exy = 5e^xy=5ex
y=e−x+4y = e^{-x} + 4y=e−x+4
y=5−xy = 5 - xy=5−x